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From: "Martin Dowie" <martin.dowie@baesystems.com>
Newsgroups: comp.lang.ada
References: <99cjt2$v9g@newsserv.vs.dasa.de>
Subject: Re: Should this be legal?
Date: Thu, 22 Mar 2001 11:15:44 -0000
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ObjectAda 7.2 SE returns the following errors:
subtype_discriminant.ads: Error: line 15 col 13 LRM:3.9.2(13), a primitive
subprogram of a tagged type may not be declared after the type is frozen

subtype_discriminant.ads: Error: line 15 col 13 LRM:3.9.2(10), return
subtype does not statically match the first subtype of the tagged type

subtype_discriminant.ads: Error: line 17 col 33 LRM:3.2.2(4), Only a
subtype_mark is permitted in this context; no constraint is allowed,
ignoring constraint

subtype_discriminant.ads: Error: line 17 col 13 LRM:3.9.2(13), a primitive
subprogram of a tagged type may not be declared after the type is frozen


Oliver Kellogg <oliver.kellogg@vs.dasa.de> wrote in message
news:99cjt2$v9g@newsserv.vs.dasa.de...
> Hello Ada experts,
>
> The full declaration of the Derived type looks different than
> the partial view (Base_2 vs. Base(2))
>
> Should this be legal?
> Rational Apex 3.2.0b and GNAT 3.13p both accept it.
> (However, both compilers tend to have problems with this
> type of construction - especially in more complicated contexts.)
>
> But then, if Base_2 and Base(2) are supposedly interchangeable,
> how come the function Legal is accepted but function Illegal is
> refused ("constraint not allowed here") ?
>
> Thanks,
>
> Oliver M. Kellogg
>
>
> -- subtyped_discriminant.ads
>
> package Subtyped_Discriminant is
>
>    type Base (N : Integer) is tagged null record;
>
>    subtype Base_2 is Base (2);
>
>    type Derived is new Base_2 with private;
>
> private
>
>    type Derived is new Base (2) with null record;
>
>    -- However,
>
>    function Legal return Base_2;
>
>    function Illegal return Base (2);
>
> end Subtyped_Discriminant;
>
>
>
>